Aquascape Medium Density Filter Mats provide efficient mechanical and biological filtration for your pond. The filter mat measures 24-inches by 39-inches and can be easily cut to your desired size and shape using a serrated knife, allowing for installation in a wide variety of skimmer boxes and filters. Aquascape Medium Density Filter Mats are 1.5-inches thick and extremely easy to maintain, only needing to be cleaned periodically.